Process of spinning artificial silk



Pa tented July -14, 1942 rnoonss or SPINNING ARTIFICIAL SILK Ewald Kneheand Franz Hoelkeskamp, Wupper-' tal-Barmen, Germany, assignors toAmerican Bemberg (iorporation, New York, N. Y., a corporation ofDelaware Application May 17, 1938, Serial No. 208,494 In Germany May 20,1937 4 Claims.

The present invention relates to the manufacture of regeneratedcellulose in the form of threads, etc., from cuprammonium cellulosesolutions in accordance with the stretch spinning process.

In the manufacture of artificial threads, such as artificial silk,staple fibre and the like from cuprammonium cellulose solutions thethreads are conventionally extruded through spinning nozzles, havingopenings of approximately from 0.8 to 1 mm. diameter, into funnels whichare continuously supplied-with soft wash water to coagulate the same.Hitherto it has only been possible to spin these threads atcomparatively low spinning speeds and in most instances this speed hasnot exceeded 30 meters per minute.

Furthermore, to spin at those speeds it has been necessary to employcomparatively large quantities of wash water for a satisfactorycoagulationof the threads. Thus about 750 cc. of water are used perminute to spin a cuprammonium cellulose thread of about 120 denier.Additional disadvantages of the conventional cuprammonium spinningprocess are high-costs of softening the wash water, the maintenance ofthis water before being used in the funnels at a temperature of about 35C., and the precipitation of copper hydroxide, etc., in the lower partof the spinning funnel, these precipitations not only impairing thetransparency of the funnel and in turn the control of the spinningprocess per se but also injuring the formed thread at the lower portionof the spinning. funnel.

It is therefore the primary object of our invention to provide a processwhich greatly reduces the amounts of wash water necessary for thecoagulation of threads produced from cuprammonium cellulose solutions.

Another object-of our invention relates to a process permitting alowering of the temperature of the wash water.

A third object is the provision of a process which prevents theprecipitation of copper salts, etc., in the lower part of the spinningfunnel.

A fourth object has to do with a process allowing acceleration of thespinning speeds heretofore used in the art, this acceleration resultingin a greater economy of the cuprammonium.

process.

These and other objects will become apparent to those skilled in the artfrom a study of the following specification.

The dr 'ng illustrates an apparatus capable of carrgfi g out the presentmethod.

Specifically in the drawing, numeral I denotes a cuprammonium spinningcell having a spinneret 2 mounted therein through which cuprammoniumcellulose solution is extruded. Coagulating fluid, such as pure water,is-introduced into a glass cylindrical casing 3 surrounding thespinneret through conduit 4 and the flow of water is such that it willfill the casing and overflow into funnel 5, contacting the filaments 6as they are drawn through the funnel.

A second funnel-like member I is position f in the bottom wall 8 of thecasing and is pr vided with a fluid inlet 9 through which salt 50-lution is introduced into the space between the lower portion of theupper funnel 5 and the lower funnel I. The upper funnel 5 is retained inspaced relation to the lower funnel I by means of a perforated ring orgasket l0 having openings ll therein, so that the water introduced intothe casing 3 flows downwardly through the lower funnel and in contactwith the thread after it leaves the upper funnel. The salt solutionintroduced into the lower funnel stratifies in the coagulating fluidand, therefore, the spinning bath includes an upper stratum ofsubstantially pure water and a lower stratum of a solution comprisingwater and a salt as will be hereinafter described in detail.

We have found by experimentation that the cuprammonium cellulosespinning process may be improved by using a stratified spinning bath inthe spinning funnels, this bath being produced by continuously injectinginto the lower portion of the spinning funnel a dilute solution of twoor more chemically different salts, such as magnesium and ammoniumcompounds; provided the concentration of this solution is carefullycontrolled to avoid visible precipitations of copper and magnesiumcompounds in the funnel. For this purpose we may use a combination ofany ammonium salt with any magnesium salt provided this combination doesnot result in precipitations .by chemical interaction. Thus, forexnesium. hydroxide by theammonium contained ample, ammonium phosphateand ammonium arsenate cannot be used in accordance with the presentinvention. We have found that a solution containing magnesium sulfateand ammo nium carbonate is very suitable for being injected into thelower portion of the spinning funneh When this mixture is used, aportion of the magnesium sulfate is converted into colloidal magin thewash water, this wash water comprising the upper stratum of the bathcontained in the funnel The concentration of these salts and theirratios must be so selected that the magne- 2. sium hydroxide formed inthe spinning funnel fails to cause a visible turbidity of the spinningwater. By injecting such a solution into the lower portion of thespinning funnel in comparatively small amounts, such as for example,80cc. per minute, it is possible to reduce the amount of spinninglwater(conventionally about 750 cc. per minute) to approximately 400 cc. perminute without deleteriously affecting the spinning process. Inaddition, besides reducing the quantity of wash water, it is alsopossible to reduce .the temperature thereof: Thus, the temperature andammonium salt may be used in'this process with the exception of ammoniumphosphate and ammonium arsenate. Magnesium chloride, am-

monium carbonate, ammonium sulfate and ammonium acetate are examples ofcompounds which may be used in the present process, although we wish toemphasize that these 'examples are merely given to illustrateourinvention and that we do not wish to be limited to the use. of thesecompounds and no others.

We have found by experimentation that it is necessary to inject thesedilute salt mixtures into the lower portion of the spinning. funnel withthe formation of colloidal magnesium hydroxide, and we wish to emphasizethat solutions of low concentration give the desired results. About 2.4g. of magnesium sulfate per liter of water is generally suflicient whilethe concentration of ammonium carbonate, etc., may be lower than that ofthe magnesium sulfate.

We have also found that it is possible to partially produce the dilutesalt mixture in the lower portion of the spinning funnel itself. Thismay be accomplished, for example, by preparing outside of the spinningfunnel a specific solution of a magnesium salt, particularly ofmagnesium sulfate, and' an acid or an acid salt. It is not necessary tofeed the magnesium salt and the acid or acid salt to the spinning funnelin the form of finished mixture, since it suflices that theaforementionel salts and/or acids be present in the lower portion of thespinning funnel in such a concentration that the desired formation ofmagnesium hydroxide in the spinning funnel takes place to such an extentthat no visible precipitation thereof occurs therein.

Example I .-A cuprammonium cellulose solution is spun through a spinningnozzle containe ing 90 holes of about 0.8 mm. diameter into aconventional funnel provided with a lower inlet for the magnesium saltmixture. Soft water of about 26 C. is introduced in conventional mannerinto an upper inlet of the funnel at the rate of about 400 cc. perminute. A salt solution of about 26 C. containing about 2.4 g. ofmagnesium sulfateand about 1.25 g. of ammonium carbonate per liter ofwater is injected into the lower inlet of the funnel at the rate ofabout 80 cc. per minute. The thread issuing at the .lower portion of.thespinning funnel is led in conventional manner over thread guides where--by the major portion of the spinning water sepaartificial silk producedin this manner has a dry strength of about 200 g. per 100 denier and awet strength of about 140 g. per 100 denier.

Example II.The identical solution is spun with the identical arrangementas set forth in Example I at a spinning speed of 62 meters per minute.400 cc. of water are injected per minute into the upper part of thefunnel, vthis water having a temperature of about 30, C. A dilutesolution of magnesium sulfate and ammonium carbonate is injected at aspeed of cc. per minute intq the lower portion of the funnel. Thissolution contains 2.5 g. of magnesium sulfate and 1.25 g. of ammoniumcarbonate per liter.

Example II I.-Cuprammonium cellulose is spun following Example I, at aspeed of 31 meters per minute with the exception that the.

injected solution contains 2.5 g. of magnesium sulfate and 1.87 g. ofammonium acetate per liter.

Example IV.Cuprammonium cellulose is spun in accordance with the processset forth in Example I, at a speed of 31 meters per minute with theexception that the injected solution contains 2.5 g. of magnesiumsulfate and 3.7 g. of potassium bisulfate per liter of water.

Example V.-Cuprammonium cellulose'is spun,-

following Example I, at a speed of 31' meters per minute and atemperature of about 28 C., with the exception that the injected liquidcontains 2.5 g. of magnesium sulfate and 1.8 g. of ammonium sulfate perliter of water..

' Example VI.Cuprammonium cellulose is spun, following Example I, at aspeed of about 31 meters per minute, with the exception that a liquid isinjected containing 2.5 g. of magnesium sulfate and 1.33 g.'of sulfuricacid per liter of Water.

the spinning of threads of 120 denier at a speed of about from"30 to 62meters per minute, a bath consumption of 400 to 480 cc. per minute, andan injectidn of salt solution containing about 0.04

to 0.05% of magnesium sulfate, calculated on the total consumption ofspinning water it must be emphasized that titers, other spinning waterquantities and differently formed spinning funnels, etc., require achange of concentration'of the injected salt solutions. Theseconcentrations and amounts of injected salt solutions must bepredetermined by experiments.

Having thus described our invention as required by the Patent Statuteswhat we claim is 1. In the process of producing artificial silk by thestretch-spinning process, the step which comprises continuouslyextruding at a speed of about 30 meters per minute a cuprammoniumcellulose solution through a spinneret having approximately openings ofabout 0.8 mm. diameter each, into the top of a funnel provided with anupper and a lower inlet, said upper inlet being furnished with about 400cc. of water per minute of about 26 0., and said lower inlet beingfurnished with about'80 cc. per minute of water of about 26 C.containing about 0.24% of magnesium sulfate and about'0.125% of am-;eter each into the topof a funnel provided with While theaforementioned examples set forth.

-nesium sulfate and about an upper and a; lower inlet, said upper inletbeing furnished-with about 400 cc. of water per minute of about 30 C.,-and said lower inlet being furnished with about 80 cc. per minute ofwater of about 30 C. containing about 0.25% of mag- 0.18% of ammoniumsulfate by weight. I

3. In the proces of producing artificial silk by continuously extrudingwith stretching a cuprammonium cellulose solution into a funnel, thestep which comprises extruding a cuprammon'i um cellulose solutionthrough a 'spinneret into/the top of a funnel provided with an upper anda lower inlet, continuously supplying water to said extruded solutionthrough said upper inlet and continuously supplying a mixture comprisingan aqueous solution of an ammonium salt and an aqueous solution of saltto said extruded solution through said lower inlet whereby theformationof a visible precipitate of copper salts, is prevented, the amamagnesium t v 3 monium salt used being chemically non-reactive with saidmagnesium salt to prevent formation 7 of a visible precipitate.

4. In the process of producing artificial silk by continuously extrudingwith stretching a cuprammonium cellulose solution through a spin!/ 'eretinto the top of a funnel provided with an upper and a lower inlet,continuously, supplying water to said extruded solution through saidupper inlet and continuously supplying a. mixture comprising an aqueoussolution of an ammonium salt and an aqueous solution of an inorganicmagnesium salt to said extruded solution through said lower inletwhereby the formation of a visible precipitate of copper salts isprevented, the ammonium salt used being chemically non-reactive withsaid magnesium salt to prevent formation of a visibleprecipitate.

EWALD KNEHE. FRANZ HOELKESKAMP.

